<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
  //1.创建核心对象
  var xhttp;
  if (window.XMLHttpRequest) {
    xhttp = new XMLHttpRequest();
  } else {
    // code for IE6, IE5
    xhttp = new ActiveXObject("Microsoft.XMLHTTP");
  }
  //2.发送请求
  xhttp.open("GET", "http://localhost:8080/ajax/AjaxServlet", true);
  xhttp.send();
  //3.获取响应
  xhttp.onreadystatechange = function() {
      if (this.readyState == 4 && this.status == 200) {
          //document.getElementById("demo").innerHTML =
              alert(this.responseText);
      }
  };
</script>
</body>
</html>